Irregular and/or abnormal inflammation is a major component of a wide range of human diseases. People suffering from multiple degenerative disorders often exhibit excess levels of pro-inflammatory markers in their blood. One type of such pro-inflammatory markers are pro-inflammatory mark cytokines including IL-1α, β, IL-2, IL-3, IL-6, IL-7, IL-9, IL-12, IL-17, IL-18, TNF-α, LT, LIF, Oncostatin, and IFNc1α, β, γ.
A non-limiting list of common medical problems that are directly caused by inflammatory cytokines include: arthritis where inflammatory cytokines destroy lead to lesion in the synovial membrane and destruction of joint cartilage and bone; kidney failure where inflammatory cytokines restrict circulation and damage nephrons; lupus wherein inflammatory cytokines induce an autoimmune attack; asthma where inflammatory cytokines close the airway; psoriasis where inflammatory cytokines induce dermatitis; pancreatitis where inflammatory cytokines induce pancreatic cell injury; allergy where inflammatory cytokines induce autoimmune reactions; fibrosis where inflammatory cytokines attack traumatized tissue; surgical complications where inflammatory cytokines prevent healing; anemia where inflammatory cytokines attack erythropoietin production; and fibromyalgia where inflammatory cytokines are elevated in fibromyalgia patients. Other diseases associated with chronic inflammation include cancer, which is caused by chronic inflammation; heart attack where chronic inflammation contributes to coronary atherosclerosis; Alzheimer's disease where chronic inflammation destroys brain cells; congestive heart failure where chronic inflammation causes heart muscle wasting; stroke where chronic inflammation promotes thrombo-embolic events; and aortic valve stenosis where chronic inflammation damages heart valves. Arteriosclerosis, osteoporosis, Parkinson's disease, infection, inflammatory bowel disease including Crohn's disease and ulcerative colitis as well as multiple sclerosis (a typical autoimmune inflammatory-related disease) are also related to inflammation (1-18). Some diseases in advanced stages can be life threatening. Several methodologies are available for the treatment of such inflammatory diseases; the results, however, are generally unsatisfactory as evidenced by a lack of efficacy and drug related side effects associated therewith.
Inflammatory Bowel Disease
Inflammatory bowel disease (IBD) comprises Crohn's disease (CD) and ulcerative colitis (UC), both of which are idiopathic chronic diseases occurring with an increasing frequency in many parts of the world. In the United States, more than 600,000 are affected every year. IBD can involve either or both small and large bowel. CD can involve any part of the gastrointestinal tract, but most frequently involves the distal small bowel and colon. It either spares the rectum, or causes inflammation or infection with drainage around the rectum. UC usually causes ulcers in the lower part of the large intestine, often starting at the rectum. Symptoms vary but may include diarrhea, fever, and pain. Patients with prolonged UC are at an increased risk of developing colon cancer.
There is currently no satisfactory treatment, as the cause for IBD remains unclear although infectious and immunologic mechanisms have been proposed. IBD treatments aim at controlling inflammatory symptoms, conventionally using corticosteroids, aminosalicylates and standard immunosuppressive agents such as azathioprine (6-mer-captopurine), methotrexate and ciclosporine. Of these, the only disease-modifying therapies are the immunosuppressive agents azathioprine and methotrexate, both of which have a slow onset of action and only a moderate efficacy. Long-term therapy may cause liver damage (fibrosis or cirrhosis) and bone marrow suppression. Also patients often become refractory to such treatment. Other therapeutic regimes merely address symptoms (19, 20).
Psoriasis
Psoriasis is one of the most common immune-mediated chronic skin diseases that come in different forms and varied levels of severity, affecting approximately 2% or more than 4.5 million people in the United States of which 1.5 million are considered to have a moderate to severe form of the disease. Ten to thirty percent of patients with psoriasis also develop a form of arthritis—Psoriatic arthritis, which damages the bone and connective tissue around the joints. Psoriasis appears as patches of raised red skin covered by a flaky white buildup. It may also have a pimple-ish (pustular psoriasis) or burned (erythrodermic) appearance. Psoriasis may also cause intense itching and burning. Patients suffer psychologically as well as physically. Several modalities are currently available for treatment of psoriasis, including topical treatment, phototherapy, and systemic applications. However, they are generally considered to be only disease suppressive and disease modifying. And none of them are curative. Moreover, many treatments are either cosmetically undesirable, inconvenient for long-term use, or associated with significant toxicity.
With increased understanding of the biological properties of psoriasis over the past 2 decades, biologic therapies targeting the activity of T lymphocytes and cytokines responsible for the inflammatory nature of this disease have become available. Currently, drugs prescribed for psoriasis include those TNF-α inhibitors initially used for rheumatoid arthritis (RA) treatment, ENBREL® (etanercept), REMICADE® (infliximab) and HUMIRA® (adalimumab), and T-cell inhibitor AMEVIVE® (alefacept) from Biogen approved in 2002 and RAPTIVA® from (Efalizumab) from Genentech/Xoma approved in 2003 (21). AMEVIVE ALEFACEPT® is an immunoglobulin fusion protein composed of the first extracellular domain of human LFA-3 fused to the hinge, C(H)2 and C(H)3 domains of human IgG(1). It inhibits T cell proliferation through NK cells (22). RAPTIVA® is also known as anti-CD11a, a humanized monoclonal antibody which targets the T cell adhesion molecule, leukocyte function-associated antigen-1 (LFA-1). Prevention of LFA-1 binding to its ligand (ICAM-1, intercellular adhesion molecule-1) inhibits lymphocyte activation and migration, resulting in a decreased lymphocyte infiltration, thereby limiting the cascade of events eventually leading to the signs and symptoms of psoriasis (23). Potential side effects for TNF-α inhibitor, however, are severe, including development of lymphoma (24), worsening congestive heart failure, resulting in a serious infection and sepsis, and exacerbations of multiple sclerosis and central nervous system problems (25, 26). While side effects of the T-cell inhibitor of AMEVIVE®/RAPTIVA® may be more tolerable in psoriasis treatment, RAPTIVA® is an immunosuppressive agent. Immunosuppressive agents have the potential to increase the risk of infection, reactivate latent, chronic infections or increase the risk of cancer development.
Although many advances have been made in the understanding of the biological properties of psoriasis over the past 2 decades and an unconventional treatment for psoriasis has become available as described above, much of the suffering it produces is still not adequately addressed. A survey of over 40,000 American patients with psoriasis performed by the National Psoriasis Foundation in 1998 showed 79% of the younger patients felt frustrated by the ineffectiveness of their treatment. Of those with severe disease, 32% felt their treatment was not aggressive enough (27, 28).
Rheumatoid Arthritis
Rheumatoid arthritis (RA) represents another example of troublesome inflammatory disorders. It is a common chronic inflammatory-related disease characterized by chronic inflammation in the membrane lining (the synovium) of the joints and/or other internal organs. The inflammatory cells can also invade and damage bone and cartilage. The joint involved can lose its shape and alignment, resulting in loss of movement. Patients with RA have pain, stiffness, warmth, redness and swelling in the joint, and other systemic symptoms like fever, fatigue, and anemia. Approximately 1% of the population or 2.1 million in the U.S. are currently affected, of which more are women (1.5 million) than men (0.6 million). The pathology of RA is not fully understood although the cascade of improper immunological reactions has been postulated as a mechanism. Conventional treatment is unfortunately inefficient in RA (29). The disease does not respond completely to symptomatic medications including corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) used since the 1950s. Also, these medications carry a risk of serious adverse effects. The therapeutic effects of the disease-modifying antirheumatic drugs (DMARDs) such as Methotrexate (MTX) are often inconsistent and short-lived.
A new class of biologic DMARDs (disease-modifying antirheumatic drugs) for the treatment of RA has recently been developed based on understanding of the role of cytokines, TNF-α and IL-1, in the inflammatory process. The FDA has approved several such DMARDs including ENBREL® (etanercept) from Immunex/Amgen Inc. in 1998, REMICADE® (infliximab) from Centocor/Johnson & Johnson, HUMIRA® (adalimumab) from Abbott Laboratories Inc. in 2002, and KINERET® (anakinra) from Amgen in 2001. ENBREL® is a soluble TNF receptor (TNFR) recombinant protein. REMICADE® is a humanized mouse (chimeric) anti-TNF-α monoclonal antibody. HUMIRA® is a fully human anti-TNF monoclonal antibody created using phage display technology resulting in an antibody with human-derived heavy and light chain variable regions and human IgG1:k constant regions. All these 3 protein-based drugs target and bind to TNF-α to block the effects of TNF-α. KINERET® is a recombinant IL-1 receptor antagonist, which is similar to native human IL-1Ra, except for the addition of a single methionine residue at its amino terminus. KINERET® blocks the biologic activity of IL-1 by competitively inhibiting IL-1 binding to the IL-1 type I receptor (IL-1RI) and consequently reducing the pro-inflammatory effects of IL-1.
The treatment with these biologic DMARDs relieves symptoms, inhibits the progression of structural damage, and improves physical function in patients with moderate to severe active RA. The 3 marketed TNF-α blocking agents have similar efficacy when combined with MTX, a widely used DMARD, in the treatment of patients with RA (30). While providing significant efficacy and a good overall safety profile in the short and medium term in many patients with RA, these biologic treatments may create serious problems and long-term side effects, such as on the liver, and still need to be evaluated. There has been a disturbing association between the use of both of ENBREL® or REMICADE® and the development of lymphoma (24). As described above, several reports have shown that patients treated with ENBREL® or REMICADE® worsen their congestive heart failure and develop serious infection and sepsis, and increase exacerbations of multiple sclerosis and other central nervous system problems (26, 27).
Multiple Sclerosis
Multiple Sclerosis (MS) is an autoimmune disease diagnosed in 350,000 to 500,000 people in the United States. Multiple areas of inflammation and scarring of the myelin in the brain and spinal cord signify the disease. Patients with MS exhibit varied degrees of neurological impairment depending on the location and extent of the scarring of the myelin. Common symptoms of MS include fatigue, weakness, spasticity, balance problems, bladder and bowel problems, numbness, vision loss, tremors and depression. Current treatment of MS only alleviates symptoms or delays the progression of disability, and several new treatments for MS including stem cell transplantation and gene therapy are conservatory (31, 32). While anti-TNF antibodies have shown protective effects in experimental autoimmune encephalomyelitis (EAE), they aggravate the disease in MS patients, suggesting that inhibition of TNF-α alone is not sufficient (33).
Neurodegenerative Disorders
Alzheimer's disease (AD) and Parkinson's disease (PK) are the 2 most common neurodegenerative disorders. AD is a brain disorder. It seriously affects a person's ability to carry out daily activities. It involves the parts of the brain that control thought, memory, and language. About 4 million Americans, usually after age 60, are estimated to suffer from AD.
PK is a progressive disorder of the central nervous system affecting over 1.5 million people in the United States. Clinically, the disease is characterized by a decrease in spontaneous movements, gait difficulty, postural instability, rigidity and tremor. PK is caused by the degeneration of the pigmented neurons in the substantia nigra of the brain, resulting in decreased dopamine availability. The causes of these neurodegenerative disorders are unknown and there is currently no cure for the disease.
Thus, novel approaches for the treatment of the above and other inflammatory-related diseases are needed. Although the mechanisms by which inflammatory-related diseases are caused remain unclear, and often vary from each other, dysfunction of the immune system caused by deregulation of cytokines has been demonstrated to play an important role in the initiation and progression of inflammation (Table 1) (27, 34, 35).
Cytokines can be generally classified into 3 types: pro-inflammatory (IL-1α, β, IL-2, IL-3, IL-6, IL-7, IL-9, IL-12, IL-17, IL-18, TNF-α, LT, LIF, Oncostatin, and IFNc1α, β, γ); anti-inflammatory (IL-4, IL-10, IL-11, W-13 and TGFβ); and chemokines (IL-8, Groα, MIP-1, MCP-1, ENA-78, and RANTES).
In many inflammatory conditions, pro-inflammatory cytokines, especially TNF-α, IL-1β, and IL-6, as well as anti-inflammatory cytokine IL-10 appear to play an important role in the pathogenesis of various inflammatory-related diseases and therefore may serve as potential therapeutic targets. For example, elevated levels of some pro-inflammatory cytokines (TNF-α, IFNγ, IL-1, IL-2, IL-6 and IL-12) and chemokines (IL-8, MCP-1 and RANTES) have been observed in several inflammatory-related diseases such as CD, psoriasis, RA, Grave's disease and Hashimoto's thyroiditis (34), which parallels an increase in soluble TNF receptors, IL-1 receptor antagonists and the anti-inflammatory cytokine IL-10 (36,37). IL-10 has been shown to suppress elevated pro-inflammatory cytokine production both in vitro in LPMC cultures and in vivo in patients (38). Positive response of CD patients treated with IL-10 demonstrates that there might also be an imbalance between the production of pro-inflammatory and anti-inflammatory cytokines in CD.
In summary, the approach of treating inflammatory-related diseases has undergone an evolutionary change in recent years in part as a consequence of growing concerns of the severity of these diseases and in part due to considerable progress in the understanding of the important role of cytokines in their immuno-pathogenesis. The majority of the efforts have been focused on targeting TNF-α and IL-1 (39), and several products (TNF-α inhibitors: infliximab, a monoclonal anti-TNF-α antibody; and etanercept, the p75 TNF-α receptor) are currently marketed or in clinical trials for the treatment of RA, psoriasis and IBD as mentioned above. Several other drug candidates or strategies targeting IL-1 (40), IL-6 or IL-10 are under development (40-42). These biological treatments provide significant efficacy in the short and medium term in many patients with RA (43-46). Although these drugs are well tolerated and have a good overall safety profile, active pharmaco-vigilance is needed. Based on its mechanism of action, and previous notifications of a wide variety of adverse effects, long-term risks of side effects including haematological, infectious, neurological, oncological and immunological effects need to be examined.
Strategies for targeting a single pro-inflammatory cytokine as an anti-inflammatory therapy ignore a very important fact, which is that inflammatory-related diseases involve a sophisticated cytokine network “system”. For example, chemokines, a family of immune molecules related to IL-8 contains approximately 50 ligands and 20 receptors, often acting with redundancy, thus making selection of appropriate specific antagonists not only difficult, but lacking in long-term efficacy. In addition, currently marketed products or products under development are mainly protein-based agents, which are expensive to produce and inconvenient to administer (i.e., infusion). Therefore, as functioning of the immune system is finely balanced by the activities of pro-inflammatory and anti-inflammatory mediators or cytokines, modulation of multiple pro/anti-inflammatory cytokines instead of blocking only one particular pro-inflammatory cytokine by small molecules should not only achieve better therapeutic efficacy with less side effects, but will also have the many advantages of small molecule drugs.
Based on this concept, we examined several types of small molecules to test their ability in the regulation of multiple cytokines and explored their potential clinical applications for the treatment of a variety of inflammatory-related diseases.
Meisoindigo is an indirubin derivative that has been used for the treatment of chronic myeloid leukemia (CML) in China with minor side effects (47). In our previous patent (U.S. Pat. No. 6,566,341), we demonstrated that Meisoindigo and its derivatives are active against solid tumors through their ability to inhibit cyclin-dependent kinases, induce cell differentiation and promote apoptosis. In the current invention, we show novel therapeutic activities of this class of molecules in the treatment of various inflammatory-related diseases including inflammatory bowel diseases and psoriasis in rodents as well as in humans. We demonstrate that this type of agent inhibits the secretion and expression of multiple pro-inflammatory cytokines including IL-1β, IL-6 and TNF-α in cell lines, and promotes production of anti-inflammatory cytokine IL-10. In one human case, Meisoindigo also proves very effective against IBD while no significant side effects were observed.
EP 1 079 826 to Eisenbrand et al., titled “Use of Indigoid Bisindole Derivatives for the Manufacture of a Medicament to Inhibit Cyclin Dependent Kinases,” is directed to the use of indigoid bisindole derivatives for the manufacture of a medicament for the treatment of diseases associated with the loss of proliferation control. According to EP 1 079 826, psoriasis, cardiovascular diseases, infectious diseases, nephrology, neurodegenerative disorders and viral infections are all diseases associated with the loss of cell proliferation control. EP 1 079 826 teaches that the medicament is effective at treating theses diseases associated with the loss of proliferation control by inhibiting cyclin dependent kinases (CDKs).
In contrast, Applicants discovered that isoindigo, indigo, indirubin, and derivatives thereof can be used to suppress or inhibit expression pro-inflammatory cytokines, e.g., TNF-α, IL-1 and IL-6, to treat inflammatory-related diseases associated with cytokine expression.
While certain diseases mentioned in EP 1 079 826 as being associated with the loss of cell proliferation control are also related to cytokine expression, Applicants have found that the amount of therapeutic agent required to treat these corresponding diseases by inhibiting the cytokine levels is significantly less than that required to inhibit CDKs as taught by EP 1 079 826.